Store tables without yang

[praveen-li]

- What I did

Store Tables without YANG models seperately for user warning.

- How I did it

Changes:
1.) Store Tables with YANG models seperately, so that a warning to user
can be issued with enough information.
2.) print the tables without YANG models properly in cropConfigDB().

- How to verify it

Changes:
1.) Added config for extra tables in yangTest.json.
2.) Added new test case to find tables without yang models.
3.) Move common part in a helper function.

pchaudha@be1e6e58be56:/sonic$ make -f slave.mk target/python-wheels/sonic_yang_mgmt-1.0-py2-none-any.whl
SONiC Build System

Build Configuration
"CONFIGURED_PLATFORM"             : "vs"
"CONFIGURED_ARCH"                 : "amd64"
"SONIC_CONFIG_PRINT_DEPENDENCIES" : ""
"SONIC_BUILD_JOBS"                : "1"
"SONIC_CONFIG_MAKE_JOBS"          : "24"
"SONIC_USE_DOCKER_BUILDKIT"       : ""
"USERNAME"                        : "admin"
"PASSWORD"                        : "YourPaSsWoRd"
"ENABLE_DHCP_GRAPH_SERVICE"       : ""
"SHUTDOWN_BGP_ON_START"           : ""
"ENABLE_PFCWD_ON_START"           : ""
"INSTALL_DEBUG_TOOLS"             : ""
"ROUTING_STACK"                   : "frr"
"FRR_USER_UID"                    : "300"
"FRR_USER_GID"                    : "300"
"ENABLE_SYNCD_RPC"                : ""
"ENABLE_ORGANIZATION_EXTENSIONS"  : "y"
"HTTP_PROXY"                      : ""
"HTTPS_PROXY"                     : ""
"ENABLE_SYSTEM_TELEMETRY"         : "y"
"ENABLE_RESTAPI"                  : "n"
"ENABLE_ZTP"                      : ""
"SONIC_DEBUGGING_ON"              : ""
"SONIC_PROFILING_ON"              : ""
"KERNEL_PROCURE_METHOD"           : "build"
"BUILD_TIMESTAMP"                 : ""
"BLDENV"                          : ""
"VS_PREPARE_MEM"                  : "yes"
"ENABLE_SFLOW"                    : "y"
"ENABLE_NAT"                      : "y"

pchaudha@be1e6e58be56:/sonic$ cat target/python-wheels/sonic_yang_mgmt-1.0-py2-none-any.whl.log

tests/test_sonic_yang_mgmt.py .
tests/libyang-python-tests/test_sonic_yang.py ........................

========================== 25 passed in 0.27 seconds ===========================

Test on 06/29/2020

pchaudha@server05:/home/pchaudha/srcCode/dpb_repo$ ls -l target/python-wheels/sonic_yang_mgmt-1.0-py2-none-any.whl
-rw-r--r-- 1 pchaudha pchaudha 19385 Jun 29 23:04 target/python-wheels/sonic_yang_mgmt-1.0-py2-none-any.whl
pchaudha@server05:/home/pchaudha/srcCode/dpb_repo$ date
Mon Jun 29 23:09:25 PDT 2020
pchaudha@server05:/home/pchaudha/srcCode/dpb_repo$

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)